U.S. patent application number 17/516093 was filed with the patent office on 2022-07-07 for multimode clutch assemblies having engagement status sensors.
This patent application is currently assigned to Textron Innovations Inc.. The applicant listed for this patent is Textron Innovations Inc.. Invention is credited to Charles Eric Covington, Douglas Andrew Goodwin, Eric Stephen Olson, David Andrew Prater, David Bryan Roberts, Chia-Wei Su, Michael David Trantham.
Application Number | 20220212783 17/516093 |
Document ID | / |
Family ID | |
Filed Date | 2022-07-07 |
United States Patent
Application |
20220212783 |
Kind Code |
A1 |
Goodwin; Douglas Andrew ; et
al. |
July 7, 2022 |
Multimode Clutch Assemblies having Engagement Status Sensors
Abstract
A multimode clutch assembly is positioned in a powertrain of a
rotorcraft. The clutch assembly includes a freewheeling unit having
a driving mode in which torque applied to the input race is
transferred to the output race and an overrunning mode in which
torque applied to the output race is not transferred to the input
race. A bypass assembly has an engaged position that couples the
input and output races of the freewheeling unit. An actuator
assembly shifts the bypass assembly between engaged and disengaged
positions. An engagement status sensor is configured to determine
the engagement status of the bypass assembly. In the disengaged
position, the overrunning mode of the freewheeling unit is enabled
such that the clutch assembly is configured for unidirectional
torque transfer. In the engaged position, the overrunning mode of
the freewheeling unit is disabled such that the clutch assembly is
configured for bidirectional torque transfer.
Inventors: |
Goodwin; Douglas Andrew;
(Fort Worth, TX) ; Prater; David Andrew; (Hurst,
TX) ; Olson; Eric Stephen; (Fort Worth, TX) ;
Roberts; David Bryan; (Bedford, TX) ; Su;
Chia-Wei; (Lewisville, TX) ; Trantham; Michael
David; (Arlington, TX) ; Covington; Charles Eric;
(Colleyville, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Textron Innovations Inc. |
Providence |
RI |
US |
|
|
Assignee: |
Textron Innovations Inc.
Providence
RI
|
Appl. No.: |
17/516093 |
Filed: |
November 1, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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17063712 |
Oct 5, 2020 |
11174015 |
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17516093 |
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16567086 |
Sep 11, 2019 |
10793284 |
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17063712 |
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16274520 |
Feb 13, 2019 |
10788088 |
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16567086 |
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62801621 |
Feb 5, 2019 |
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International
Class: |
B64C 27/12 20060101
B64C027/12; B64D 35/08 20060101 B64D035/08; F16D 41/04 20060101
F16D041/04 |
Goverment Interests
GOVERNMENT RIGHTS
[0002] This invention was made with Government support under
Agreement No. W911W6-19-9-0002, awarded by the Army Contracting
Command-Redstone Arsenal. The Government has certain rights in the
invention.
Claims
1. A multimode clutch assembly for a rotorcraft, the clutch
assembly comprising: a freewheeling unit having an input race and
an output race, the freewheeling unit having a driving mode in
which torque applied to the input race is transferred to the output
race and an overrunning mode in which torque applied to the output
race is not transferred to the input race; a bypass assembly having
an engaged position in which the bypass assembly couples the input
and output races of the freewheeling unit and a disengaged position
in which the bypass assembly does not couple the input and output
races of the freewheeling unit; an actuator assembly having an
engagement configuration supplying an engagement force to shift the
bypass assembly from the disengaged position to the engaged
position and a disengagement configuration supplying a
disengagement force to shift the bypass assembly from the engaged
position to the disengaged position, the actuator assembly
including a liner, a piston and a bearing sled, the piston slidably
disposed relative to the liner, the bearing sled coupled between
the piston and the bypass assembly; and an inductive proximity
sensor operably associated with the actuator assembly, the
inductive proximity sensor configured to monitor the position of
the bearing sled relative thereto to determine an engagement status
of the bypass assembly; wherein, in the disengaged position of the
bypass assembly, the overrunning mode of the freewheeling unit is
enabled such that the clutch assembly is configured for
unidirectional torque transfer from the input race to the output
race; and wherein, in the engaged position of the bypass assembly,
the overrunning mode of the freewheeling unit is disabled such that
the clutch assembly is configured for bidirectional torque transfer
between the input and output races.
2. The clutch assembly as recited in claim 1 wherein the engagement
force is configured to shift the bypass assembly from the
disengaged position to the engaged position when the disengagement
force is not provided.
3. The clutch assembly as recited in claim 1 wherein the actuator
assembly further comprises a mechanical biasing element configured
to provide the engagement force.
4. The clutch assembly as recited in claim 1 wherein the actuator
assembly further comprises a pressurized lubricating oil configured
to provide the engagement force.
5. The clutch assembly as recited in claim 1 wherein the actuator
assembly further comprises a pressure switch configured to
selectively provide the disengagement force.
6. The clutch assembly as recited in claim 5 wherein the pressure
switch further comprises a hydraulic switch.
7. The clutch assembly as recited in claim 5 wherein the pressure
switch further comprises a compressed air switch.
8. The clutch assembly as recited in claim 1 wherein the actuator
assembly further comprises an electric switch configured to
selectively provide the disengagement force.
9. The clutch assembly as recited in claim 1 wherein the actuator
assembly is in a default configuration when the disengagement force
is not provided.
10. A multimode clutch assembly for a rotorcraft, the clutch
assembly comprising: a freewheeling unit having an input race and
an output race, the freewheeling unit having a driving mode in
which torque applied to the input race is transferred to the output
race and an overrunning mode in which torque applied to the output
race is not transferred to the input race; a bypass assembly having
an engaged position in which the bypass assembly couples the input
and output races of the freewheeling unit and a disengaged position
in which the bypass assembly does not couple the input and output
races of the freewheeling unit; an actuator assembly having an
engagement configuration supplying an engagement force to shift the
bypass assembly from the disengaged position to the engaged
position and a disengagement configuration supplying a
disengagement force to shift the bypass assembly from the engaged
position to the disengaged position; and a variable differential
transformer operably associated with at least one of the bypass
assembly and the actuator assembly, the variable differential
transformer configured to determine an engagement status of the
bypass assembly; wherein, in the disengaged position of the bypass
assembly, the overrunning mode of the freewheeling unit is enabled
such that the clutch assembly is configured for unidirectional
torque transfer from the input race to the output race; and
wherein, in the engaged position of the bypass assembly, the
overrunning mode of the freewheeling unit is disabled such that the
clutch assembly is configured for bidirectional torque transfer
between the input and output races.
11. The clutch assembly as recited in claim 10 wherein the variable
differential transformer further comprises a linear variable
differential transformer.
12. The clutch assembly as recited in claim 10 wherein the variable
differential transformer further comprises a rotary variable
differential transformer.
13. The clutch assembly as recited in claim 10 wherein the
engagement force is configured to shift the bypass assembly from
the disengaged position to the engaged position when the
disengagement force is not provided.
14. The clutch assembly as recited in claim 10 wherein the actuator
assembly further comprises a mechanical biasing element configured
to provide the engagement force.
15. The clutch assembly as recited in claim 10 wherein the actuator
assembly further comprises a pressurized lubricating oil configured
to provide the engagement force.
16. The clutch assembly as recited in claim 10 wherein the actuator
assembly further comprises a pressure switch configured to
selectively provide the disengagement force.
17. The clutch assembly as recited in claim 16 wherein the pressure
switch further comprises a hydraulic switch.
18. The clutch assembly as recited in claim 16 wherein the pressure
switch further comprises a compressed air switch.
19. The clutch assembly as recited in claim 10 wherein the actuator
assembly further comprises an electric switch configured to
selectively provide the disengagement force.
20. The clutch assembly as recited in claim 10 wherein the actuator
assembly is in a default configuration when the disengagement force
is not provided.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of co-pending
application Ser. No. 17/063,712, filed Oct. 5, 2020, which is a
continuation-in-part of application Ser. No. 16/567,086, filed Sep.
11, 2019, which is a continuation-in-part of application Ser. No.
16/274,520, filed Feb. 13, 2019, which claims the benefit of
provisional application Ser. No. 62/801,621, filed Feb. 5, 2019,
the entire contents of each are hereby incorporated by
reference.
TECHNICAL FIELD OF THE DISCLOSURE
[0003] The present disclosure relates, in general, to clutch
assemblies operable for use on rotorcraft and, in particular, to
multimode clutch assemblies having engagement status sensors that
are operable to enable the selective use of secondary engine power
independent of or together with main engine power to drive the main
rotor, the tail rotor and/or the accessories of a rotorcraft.
BACKGROUND
[0004] Many rotorcraft are capable of taking off, hovering and
landing vertically. One such rotorcraft is a helicopter, which has
a main rotor that provides lift and thrust to the aircraft. The
main rotor not only enables hovering and vertical takeoff and
landing, but also enables forward, backward and lateral flight.
These attributes make helicopters highly versatile for use in
congested, isolated or remote areas. It has been found that the
power demand of a rotorcraft can vary significantly based upon the
operation being performed. For example, low power demand exists
during preflight operations, when power is only needed to operate
accessories such as generators, air pumps, oil pumps, hydraulic
systems and the like as well as to start the main engine. Certain
rotorcraft utilize a dedicated auxiliary power unit to generate
preflight accessory power. During takeoff, hover, heavy lifts
and/or high speed operations, rotorcraft experience high power
demand. Certain rotorcraft utilize multiple main engines or one
main engine and a supplemental power unit to generate the required
power for the main rotor during such high power demand flight
operations. In conventional rotorcraft, the dedicated auxiliary
power unit is not operable to provide supplemental power to the
main rotor during high power demand flight operations. Accordingly,
a need has arisen for improved rotorcraft systems that enable an
auxiliary power unit to not only provide accessory power during
preflight operations but also to operate as a supplemental power
unit to provide power to the main rotor during high power demand
flight operations.
SUMMARY
[0005] In a first aspect, the present disclosure is directed to a
multimode clutch assembly for a rotorcraft. The clutch assembly
includes a freewheeling unit having an input race and an output
race. The freewheeling unit has a driving mode in which torque
applied to the input race is transferred to the output race and an
overrunning mode in which torque applied to the output race is not
transferred to the input race. A bypass assembly has an engaged
position in which the bypass assembly couples the input and output
races of the freewheeling unit and a disengaged position in which
the bypass assembly does not couple the input and output races of
the freewheeling unit. An actuator assembly has an engagement
configuration supplying an engagement force to shift the bypass
assembly from the disengaged position to the engaged position and a
disengagement configuration supplying a disengagement force to
shift the bypass assembly from the engaged position to the
disengaged position. An engagement status sensor is operably
associated with at least one of the bypass assembly and the
actuator assembly. The engagement status sensor is configured to
determine an engagement status of the bypass assembly. In the
disengaged position of the bypass assembly, the overrunning mode of
the freewheeling unit is enabled such that the clutch assembly is
configured for unidirectional torque transfer from the input race
to the output race. In the engaged position of the bypass assembly,
the overrunning mode of the freewheeling unit is disabled such that
the clutch assembly is configured for bidirectional torque transfer
between the input and output races.
[0006] In some embodiments, the engagement status sensor may be a
proximity sensor. In such embodiments, the actuator assembly may
include a liner, a piston and a bearing sled wherein the piston is
slidably disposed relative to the liner and the bearing sled is
coupled between the piston and the bypass assembly and wherein the
proximity sensor may be an inductive proximity sensor configured to
monitor the position of the bearing sled relative thereto to
determine the engagement status of the bypass assembly.
Alternatively, the proximity sensor may be a load cell, such as a
strain sensor, that is configured to monitor the position of the
bypass assembly relative thereto to determine the engagement status
of the bypass assembly. In certain embodiments, the engagement
status sensor may be an oil pressure sensor. In some embodiments,
the engagement status sensor may be a tooth passage frequency
sensor such as a variable reluctance sensor or a hall-effect
sensor. In other embodiments, the engagement status sensor may be a
variable differential transformer such as a linear variable
differential transformer or a rotary variable differential
transformer.
[0007] In a second aspect, the present disclosure is directed to a
powertrain for a rotorcraft. The powertrain has a main drive system
including a main engine. The powertrain also has a secondary engine
and a multimode clutch assembly that is positioned between the main
drive system and the secondary engine. The clutch assembly includes
a freewheeling unit having an input race coupled to the main drive
system and an output race coupled to the secondary engine. The
freewheeling unit has a driving mode in which torque applied to the
input race is transferred to the output race and an overrunning
mode in which torque applied to the output race is not transferred
to the input race. A bypass assembly has an engaged position in
which the bypass assembly couples the input and output races of the
freewheeling unit and a disengaged position in which the bypass
assembly does not couple the input and output races of the
freewheeling unit. An actuator assembly has an engagement
configuration supplying an engagement force to shift the bypass
assembly from the disengaged position to the engaged position and a
disengagement configuration supplying a disengagement force to
shift the bypass assembly from the engaged position to the
disengaged position. An engagement status sensor is operably
associated with at least one of the bypass assembly and the
actuator assembly. The engagement status sensor is configured to
determine an engagement status of the bypass assembly. In the
disengaged position of the bypass assembly, the overrunning mode of
the freewheeling unit is enabled such that the clutch assembly is
configured for unidirectional torque transfer from the input race
to the output race. In the engaged position of the bypass assembly,
the overrunning mode of the freewheeling unit is disabled such that
the clutch assembly is configured for bidirectional torque transfer
between the input and output races.
[0008] In some embodiments, the main engine may be a gas turbine
engine and the secondary engine may be a gas turbine engine. In
other embodiments, the main engine may be a gas turbine engine and
the secondary engine may be an electric motor. In certain
embodiments, the secondary engine may be configured to generate
between about 5 percent and about 20 percent of the power of the
main engine or between about 10 percent and about 15 percent of the
power of the main engine.
[0009] In a third aspect, the present disclosure is directed to a
rotorcraft. The rotorcraft includes a main rotor coupled to a main
drive system including a main engine. The rotorcraft also includes
a secondary engine and a multimode clutch assembly that is
positioned between the main drive system and the secondary engine.
The clutch assembly includes a freewheeling unit having an input
race coupled to the main drive system and an output race coupled to
the secondary engine. The freewheeling unit has a driving mode in
which torque applied to the input race is transferred to the output
race and an overrunning mode in which torque applied to the output
race is not transferred to the input race. A bypass assembly has an
engaged position in which the bypass assembly couples the input and
output races of the freewheeling unit and a disengaged position in
which the bypass assembly does not couple the input and output
races of the freewheeling unit. An actuator assembly has an
engagement configuration supplying an engagement force to shift the
bypass assembly from the disengaged position to the engaged
position and a disengagement configuration supplying a
disengagement force to shift the bypass assembly from the engaged
position to the disengaged position. An engagement status sensor is
operably associated with at least one of the bypass assembly and
the actuator assembly. The engagement status sensor is configured
to determine an engagement status of the bypass assembly. In the
disengaged position of the bypass assembly, the overrunning mode of
the freewheeling unit is enabled such that the clutch assembly is
configured for unidirectional torque transfer from the input race
to the output race. In the engaged position of the bypass assembly,
the overrunning mode of the freewheeling unit is disabled such that
the clutch assembly is configured for bidirectional torque transfer
between the input and output races.
[0010] In a preflight configuration of the rotorcraft, the bypass
assembly is in the disengaged position, the main engine is not
operating and the secondary engine provides power to at least one
rotorcraft accessory. In an enhanced power configuration of the
rotorcraft, the bypass assembly is in the engaged position, the
main engine provides power to the main drive system and the
secondary engine provides power to at least one rotorcraft
accessory and to the main drive system through the clutch assembly.
In a high efficiency configuration of the rotorcraft, the bypass
assembly is in the engaged position, the secondary engine is in
standby mode and the main engine provides power to the main drive
system and to at least one rotorcraft accessory through the clutch
assembly. In an enhanced autorotation configuration of the
rotorcraft, the bypass assembly is in the engaged position, the
main engine is not operating and the secondary engine provides
power to the main drive system through the clutch assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] For a more complete understanding of the features and
advantages of the present disclosure, reference is now made to the
detailed description along with the accompanying figures in which
corresponding numerals in the different figures refer to
corresponding parts and in which:
[0012] FIGS. 1A-1C are schematic illustrations of a rotorcraft
having a multimode clutch assembly in accordance with embodiments
of the present disclosure;
[0013] FIGS. 2A-2E are block diagrams of a powertrain including a
multimode clutch assembly for a rotorcraft in various operating
configurations in accordance with embodiments of the present
disclosure;
[0014] FIGS. 3A-3C are cross sectional views of a rotorcraft
gearbox assembly including a multimode clutch assembly in various
operating configurations in accordance with embodiments of the
present disclosure;
[0015] FIGS. 4A-4B are cross sectional views of a rotorcraft
gearbox assembly including a multimode clutch assembly and
depicting a lubrication circuit in accordance with embodiments of
the present disclosure;
[0016] FIGS. 5A-5B are cross sectional views of a rotorcraft
gearbox assembly including a multimode clutch assembly in various
operating configurations in accordance with embodiments of the
present disclosure;
[0017] FIGS. 6A-6B are cross sectional views of a rotorcraft
gearbox assembly including a multimode clutch assembly in various
operating configurations in accordance with embodiments of the
present disclosure; and
[0018] FIGS. 7A-7E are cross sectional views of a rotorcraft
gearbox assembly including a multimode clutch assembly and
depicting various engagement status sensors in accordance with
embodiments of the present disclosure.
DETAILED DESCRIPTION
[0019] While the making and using of various embodiments of the
present disclosure are discussed in detail below, it should be
appreciated that the present disclosure provides many applicable
inventive concepts, which can be embodied in a wide variety of
specific contexts. The specific embodiments discussed herein are
merely illustrative and do not delimit the scope of the present
disclosure. In the interest of clarity, all features of an actual
implementation may not be described in this specification. It will
of course be appreciated that in the development of any such actual
embodiment, numerous implementation-specific decisions must be made
to achieve the developer's specific goals, such as compliance with
system-related and business-related constraints, which will vary
from one implementation to another. Moreover, it will be
appreciated that such a development effort might be complex and
time-consuming but would nevertheless be a routine undertaking for
those of ordinary skill in the art having the benefit of this
disclosure.
[0020] In the specification, reference may be made to the spatial
relationships between various components and to the spatial
orientation of various aspects of components as the devices are
depicted in the attached drawings. However, as will be recognized
by those skilled in the art after a complete reading of the present
disclosure, the devices, members, apparatuses, and the like
described herein may be positioned in any desired orientation.
Thus, the use of terms such as "above," "below," "upper," "lower"
or other like terms to describe a spatial relationship between
various components or to describe the spatial orientation of
aspects of such components should be understood to describe a
relative relationship between the components or a spatial
orientation of aspects of such components, respectively, as the
devices described herein may be oriented in any desired direction.
As used herein, the term "coupled" may include direct or indirect
coupling by any means, including by mere contact or by moving
and/or non-moving mechanical connections.
[0021] Referring to FIGS. 1A-1C in the drawings, a rotorcraft in
the form of a helicopter is schematically illustrated and generally
designated 10. The primary propulsion assembly of helicopter 10 is
a main rotor assembly 12. Main rotor assembly 12 includes a
plurality of rotor blades 14 extending radially outward from a main
rotor hub 16. Main rotor assembly 12 is coupled to a fuselage 18
and is rotatable relative thereto. The pitch of rotor blades 14 can
be collectively and/or cyclically manipulated to selectively
control direction, thrust and lift of helicopter 10. A tailboom 20
is coupled to fuselage 18 and extends from fuselage 18 in the aft
direction. An anti-torque system 22 includes a tail rotor assembly
24 coupled to an aft end of tailboom 20. Anti-torque system 22
controls the yaw of helicopter 10 by counteracting the torque
exerted on fuselage 18 by main rotor assembly 12. In the
illustrated embodiment, helicopter 10 includes a vertical tail fin
26 that provide stabilization to helicopter 10 during high speed
forward flight. In addition, helicopter 10 includes wing members 28
that extend laterally from fuselage 18 and wing members 30 that
extend laterally from tailboom 20. Wing members 28, 30 provide lift
to helicopter 10 responsive to the forward airspeed of helicopter
10, thereby reducing the lift requirement on main rotor assembly 12
and increasing the top speed of helicopter 10
[0022] Main rotor assembly 12 and tail rotor assembly 24 receive
torque and rotational energy from a main engine 32. Main engine 32
is coupled to a main rotor gearbox 34 by suitable clutching and
shafting. Main rotor gearbox 34 is coupled to main rotor assembly
12 by a mast 36 and is coupled to tail rotor assembly 24 by tail
rotor drive shaft 38. In the illustrated embodiment, a secondary
engine 40 is coupled to tail rotor drive shaft 38 by a secondary
gearbox 42. Together, main engine 32, main rotor gearbox 34, tail
rotor drive shaft 38, secondary engine 40 and secondary gearbox 42
as well as various other shafts and gearboxes coupled therein may
be considered as the powertrain of helicopter 10.
[0023] Secondary engine 40 is operable as an auxiliary power unit
to provide preflight power to the accessories of helicopter 10 such
as electric generators, air pumps, oil pumps, hydraulic systems and
the like as well as to provide the power required to start main
engine 32. In addition, secondary engine 40 is operable to provide
supplemental power to main rotor assembly 12 that is additive with
the power provided by main engine 32 during, for example, high
power demand conditions including takeoff, hover, heavy lifts and
high speed flight operations. Secondary engine 40 is also operable
to provide emergency power to main rotor assembly 12. For example,
in the event of a failure of main engine 32, secondary engine 40 is
operable to provide emergency power to enhance the autorotation and
flare recovery maneuver of helicopter 10. Use of secondary engine
40 not only enhances the safety of helicopter 10 but also increases
the efficiency of helicopter 10. For example, having the extra
power provided by secondary engine 40 during high power demand
operations allows main engine 32 to be downsized for more efficient
single engine operations such as during cruise operations.
[0024] It should be appreciated that helicopter 10 is merely
illustrative of a variety of aircraft that can implement the
embodiments disclosed herein. Indeed, the multimode clutch assembly
of the present disclosure may be implemented on any rotorcraft.
Other aircraft implementations can include hybrid aircraft,
tiltwing aircraft, tiltrotor aircraft, quad tiltrotor aircraft,
unmanned aircraft, gyrocopters, propeller-driven airplanes,
compound helicopters, drones and the like. As such, those skilled
in the art will recognize that the multimode clutch assembly of the
present disclosure can be integrated into a variety of aircraft
configurations. It should be appreciated that even though aircraft
are particularly well-suited to implement the embodiments of the
present disclosure, non-aircraft vehicles and devices can also
implement the embodiments.
[0025] Referring to FIG. 2A in the drawings, a powertrain 100 of a
rotorcraft is illustrated in a block diagram format. Powertrain 100
includes a main engine 102 such as a turbo shaft engine capable of
producing 2000 to 4000 horsepower or more, depending upon the
particular implementation. Main engine 102 is coupled to a
freewheeling unit depicted as sprag clutch 104 that acts as a
one-way clutch enabling a driving mode in which torque from main
engine 102 is coupled to main rotor gearbox 106 when the rotating
speed of the input race, on the main engine side of sprag clutch
104, is matched with the rotating speed of the output race, on the
main rotor gearbox side of sprag clutch 104. Importantly, sprag
clutch 104 has an overrunning mode in which main engine 102 is
decoupled from main rotor gearbox 106 when the rotating speed of
the input race is less than the rotating speed of the output race
of sprag clutch 104. Operating sprag clutch 104 in the overrunning
mode allows, for example, main rotor 108 of helicopter 10 to engage
in autorotation in the event of a failure of main engine 102.
[0026] In the illustrated embodiment, main rotor gearbox 106 is
coupled to sprag clutch 104 via a suitable drive shaft. In
addition, main rotor gearbox 106 is coupled to main rotor 108 by a
suitable mast. Main rotor gearbox 106 includes a gearbox housing
and a plurality of gears, such as planetary gears, used to adjust
the engine output speed to a suitable rotor speed so that main
engine 102 and main rotor 108 may each rotate at optimum speed
during flight operations of helicopter 10. Main rotor gearbox 106
is coupled to a tail rotor gearbox 110 via a suitable tail rotor
drive shaft. Tail rotor gearbox 110 includes a gearbox housing and
a plurality of gears that may adjust the main rotor gearbox output
speed to a suitable rotational speed for operation of tail rotor
112. Main engine 102, sprag clutch 104, main rotor gearbox 106 and
tail rotor gearbox 110 as well as various shafts and gearing
systems coupled therewith may be considered the main drive system
of powertrain 100.
[0027] Powertrain 100 includes a secondary engine 114 such as a
turbo shaft engine or an electric motor capable of producing 200 to
400 horsepower or more, depending upon the particular
implementation. In the illustrated embodiment, secondary engine 114
may generate between about 5 percent and about 20 percent or more
of the horsepower of main engine 102. In other embodiments,
secondary engine 114 may generate between about 10 percent and
about 15 percent of the horsepower of main engine 102. Secondary
engine 114 is coupled to a secondary gearbox 116. Secondary engine
114 and secondary gearbox 116 as well as various shafts and gearing
systems coupled therewith may be considered the secondary drive
system of powertrain 100.
[0028] Referring additionally to FIG. 3A, secondary gearbox 116
includes a freewheeling unit depicted as sprag clutch 118 that acts
as a one-way clutch enabling a driving mode in which torque from
secondary engine 114 is coupled through sprag clutch 118 from an
input race 120 to an output race 122. In the illustrated
embodiment, output race 122 is coupled to an output gear 126 that
provides power to accessories 124 such as one or more generators,
air pumps, oil pumps, hydraulic systems and the like. Sprag clutch
118 has an overrunning mode in which secondary engine 114 is
decoupled from torque transfer through sprag clutch 118 when the
rotating speed of input race 120 is less than the rotating speed of
output race 122. Operating sprag clutch 118 in the overrunning mode
allows, for example, main engine 102 to drive accessories 124 when
secondary engine 114 is in standby mode or not operating, as
discussed herein.
[0029] Secondary gearbox 116 includes a multimode clutch assembly
128 that is coaxially aligned with sprag clutch 118 and secondary
engine 114, in the illustrated embodiment. In other embodiments,
multimode clutch assembly 128 may operate on a separate axis than
sprag clutch 118 and/or secondary engine 114. Multimode clutch
assembly 128 has a unidirectional torque transfer mode and a
bidirectional torque transfer mode. In the illustrated embodiment,
multimode clutch assembly 128 includes a freewheeling unit depicted
as sprag clutch 130, a bypass assembly 132 and an actuator assembly
134. Sprag clutch 130 has an input race 136 that is coupled to main
rotor gearbox 106 via the tail rotor drive shaft and one or more
gears including input gear 138. Sprag clutch 130 has an output race
140 that is coupled to output race 122 of sprag clutch 118 via
shaft 122a. Shaft 122a has outer splines (not visible) that are
coupled to inner splines 140a of output race 140. Likewise, shaft
122a has outer splines (not visible) that are coupled to inner
splines (not visible) of output race 122. Sprag clutch 130 may act
as a one-way clutch enabling a driving mode in which torque from
the main drive system is coupled through sprag clutch 130 from
input race 136 to output race 140. Sprag clutch 130 also has an
overrunning mode in which the main drive system is decoupled from
torque transfer with sprag clutch 130 when the rotating speed of
input race 136 is less than the rotating speed of output race 140
of sprag clutch 130. When sprag clutch 130 is acting as a one-way
clutch, multimode clutch assembly 128 is in its unidirectional
torque transfer mode. In the unidirectional torque transfer mode of
multimode clutch assembly 128, torque can be driven from the main
drive system through secondary gearbox 116 but torque cannot be
driven from secondary gearbox 116 to the main drive system of
powertrain 100.
[0030] Referring additionally to FIG. 3C, the overrunning mode of
multimode clutch assembly 128 can be disabled by engaging bypass
assembly 132 to couple input race 136 and output race 140 of sprag
clutch 130 to functionally form a connected shaft. In this
configuration with bypass assembly 132 preventing sprag clutch 130
from operating in the overrunning mode, multimode clutch assembly
128 is in its bidirectional torque transfer mode. In the
bidirectional torque transfer mode of multimode clutch assembly
128, torque can be driven from the main drive system through
secondary gearbox 116 and torque can be driven from secondary
gearbox 116 to the main drive system of powertrain 100.
[0031] Multimode clutch assembly 128 is operated between the
unidirectional and bidirectional torque transfer modes by shifting
bypass assembly 132 between its disengaged position (FIG. 3A) and
its engaged position (FIG. 3C). The operations of engaging and
disengaging bypass assembly 132 may be pilot controlled and/or may
be automated by the flight control computer of helicopter 10 and
may be determined according to the operating conditions of
helicopter 10. In the illustrated embodiment, bypass assembly 132
is shifted between the engaged and disengaged positions responsive
to engagement and disengagement forces supplied by actuator
assembly 134, which may be generated mechanically, electrically,
hydraulically, pneumatically and/or combinations thereof or by
other suitable actuation signaling means.
[0032] In the illustrated embodiment, actuator assembly 134
includes an actuator liner 142 that is fixed relative to the
housing of secondary gearbox 116. A piston 144 is slidably and
sealingly received within actuator liner 142. In the illustrated
embodiment, piston 144 is coupled to a piston extension depicted as
an oil jet 146. In other embodiments, piston 144 and oil jet 146
may be integral or oil jet 146 may be omitted. Actuator assembly
134 also includes a bearing sled 148 that is slidably received
about actuator liner 142 and that slidably receives piston 144
therein. Bearing sled 148 and actuator liner 142 preferably
including an anti-rotation feature that prevents relative rotation
therebetween such as a tab and slot assembly wherein, for example,
one or more tabs of actuator liner 142 extend radially outwardly
into slots of bearing sled 148 or wherein one or more tabs of
bearing sled 148 extend radially inwardly into slots of actuator
liner 142 (not pictured). In the illustrated embodiment, a
mechanical biasing element depicted as wave spring 150 is
positioned between a shoulder of piston 144 and a shoulder bearing
sled 148. A bearing assembly depicted as a ball bearing set 152
couples bearing sled 148 with bypass assembly 132 such that bypass
assembly 132 translates with bearing sled 148 and is rotatable
relative to bearing sled 148 as well as the other components of
actuator assembly 134. In the illustrated embodiment, the inner
race of ball bearing set 152 has an anti-rotation coupling with
bearing sled 148. In addition, actuator assembly 134 includes an
actuator 154 having a cylinder 156 that is shiftable responsive to
an electric signal, a hydraulic signal, a pneumatic signal or the
like. When actuator 154 is electrically signaled, actuator 154 may
be referred to herein as an electric switch. When actuator 154 is
hydraulically or pneumatically signaled, actuator 154 may be
referred to herein as a pressure switch and more precisely a
hydraulic switch or a compressed air switch, respectively.
Operation of cylinder 156 by actuator 154 causes piston 144 to
shift relative to actuator liner 142 between first and second
positions. Shifting of piston 144 causes bypass assembly 132 to
shift between engaged and disengaged positions with sprag clutch
130. More specifically, bypass assembly 132 includes a shaft 132a
having outer splines (not visible) and a ring gear 132b having
outer splines (not visible). The outer splines of shaft 132a are in
mesh with inner splines 140a of output race 140 of sprag clutch 130
such that when output race 140 is rotating, bypass coupling 132
also rotates. The outer splines of ring gear 132b are selectively
engaged with and disengaged from inner splines 136a of input race
136 to operate multimode clutch assembly 128 between the
unidirectional and bidirectional torque transfer modes.
[0033] Returning to FIGS. 2A-2E, operating scenarios for helicopter
10 will now be described. In FIG. 2A, powertrain 100 is in a
preflight configuration in which main engine 102 is not yet
operating as indicated by the dashed lines between the components
of the main drive system. As the main drive system is not turning,
no torque is being applied to secondary gearbox 116 from the main
drive system as indicated by the dashed line therebetween. Prior to
starting secondary engine 114, an engagement status of multimode
clutch assembly 128 should be checked. In the illustrated
embodiment, an engagement status sensor includes three
circumferentially distributed inductive proximity sensors 158 (only
one being visible in FIGS. 3A-3C) that are used to determine the
engagement status of bypass assembly 132 by measuring the position
of bearing sled 148 relative to proximity sensors 158 by detecting
the presence or absence of the metal of bearing sled 148 adjacent
to the faces of proximity sensors 158. For example, as best seen in
FIG. 3C, proximity sensors 158 detect the absence of bearing sled
148 relative thereto indicating bypass assembly 132 is in the
engaged position. In addition, as best seen in FIGS. 3A and 3B,
proximity sensors 158 detect the presence of bearing sled 148
relative thereto indicating bypass assembly 132 is not in the
engaged position. In other embodiments, other numbers of proximity
sensors 158 in other orientations may be used. In still other
embodiments, other types of engagement status sensors may be used
to determine the engagement status of bypass assembly 132, as will
be discussed herein. In addition to determining the engagement
status of bypass assembly 132 in pre-flight, the use of an
engagement status sensor is also beneficial in determining, for
example, a malfunction of actuator assembly 134, breakage of wave
spring 150, partial engagement or disengagement of bypass assembly
132, disengagement of bypass assembly 132 during flight,
disengagement of bypass assembly 132 under torque, engagement of
bypass assembly 132 at a differential speed relative to outer race
136 as well as other undesirable conditions.
[0034] Following the status check, if multimode clutch assembly 128
is not in the unidirectional torque transfer mode with bypass
assembly 132 in the disengaged position, actuator 154 provides a
suitable disengagement signal (hydraulic, pneumatic, electric) to
operate cylinder 156 and shift piston 144 to the position shown in
FIG. 3A, thereby shifting bypass assembly 132 to the disengaged
position. It is noted that in the disengaged position, contact
between bypass assembly 132 and the housing of secondary gearbox
116 is prevented by bearing sled 148. Another status check may now
be performed. Following the status check, if multimode clutch
assembly 128 is in the unidirectional torque transfer mode with
bypass assembly 132 is in the disengaged position, secondary engine
114 may be started such that secondary engine 114 provides torque
and rotational energy within the secondary drive system, as
indicated by the arrows between secondary engine 114, secondary
gearbox 116 and accessories 124, in FIG. 2A. More specifically,
secondary engine 114 is driving input race 120 of sprag clutch 118,
which causes output race 122 of sprag clutch 118 to drive output
gear 126 which in turn provides power to accessories 124. It is
noted that rotation of output race 122 causes rotation of shaft
122a which in turn causes rotation of output race 140 of sprag
clutch 130, which is operation in its overrunning mode. In
addition, rotation of shaft 122a causes rotation bypass assembly
132 via inner splines 140a. While operating in the preflight
configuration, the pilot of helicopter 10 can proceed through the
startup procedure. Prior to starting main engine 102, the status of
multimode clutch assembly 128 may be checked again using proximity
sensors 158. This process step provides further assurance that
bypass assembly 132 is secured in the disengaged position prior to
starting main engine 102.
[0035] Once main engine 102 is started, torque is delivered through
the main drive system as indicated by the arrows between the
components within the main drive system, as best seen in FIG. 2B.
In addition, the main drive system may supply torque to secondary
gearbox 116, as indicated by the arrow therebetween. When power is
applied to input race 136 of sprag clutch 130 via input gear 138
from the main drive system such that input race 136 and output race
140 of sprag clutch 130 are turning together at the same speed,
multimode clutch assembly 128 may be operated from the
unidirectional torque transfer mode to the bidirectional torque
transfer mode. Specifically, bypass assembly 132 can now be shifted
from the disengaged position to the engaged position responsive to
pilot input and/or operation of the flight control computer of
helicopter 10. In the illustrated embodiment, actuator 154 provides
a suitable engagement signal (hydraulic, pneumatic, electric) to
operate cylinder 156 and shift piston 144 to the position shown in
FIG. 3B. In the illustrated configuration, the movement of piston
144 relative to actuator liner 142 and bearing sled 148 has
compressed wave spring 150 between piston 144 and bearing sled 148
due to contact between the faces of the outer splines of ring gear
132b and inner splines 136a of input race 136. Wave spring 150
assists in overcoming such misalignment in the clocking of the
outer splines of ring gear 132b and inner splines 136a of input
race 136 by allowing full actuation of piston 144 while maintaining
pressure between ring gear 132b and input race 136 so that when
bypass assembly 132 and input race 136 start to rotate relative to
each other, the outer splines of ring gear 132b will mesh with
inner splines 136a of input race 136, thereby shifting bypass
assembly 132 to the engaged position and multimode clutch assembly
128 to the bidirectional torque transfer mode, as best seen in FIG.
3C.
[0036] If the outer splines of ring gear 132b and inner splines
136a of input race 136 are aligned prior to operating cylinder 156,
bypass assembly 132 may be shifted directly from the disengaged
position (FIG. 3A) to the engaged position (FIG. 3C) without
compressing spring 150 or being in the intermediate position
depicted in FIG. 3B. In the bidirectional torque transfer mode of
multimode clutch assembly 128, when input race 136 of sprag clutch
130 is driven by the main drive system, bypass assembly 132 and
output race 140 rotate therewith. In addition, when output race 140
of sprag clutch 130 is driven by secondary engine 114, bypass
assembly 132 and input race 136 rotate therewith to supply power to
main drive system, thereby bypassing the overrunning mode of sprag
clutch 130 such that multimode clutch assembly 128 operates with
the functionality of a connected shaft. Actuator assembly 134
preferably has a suitable locking mechanism to maintain bypass
assembly 132 in the engaged position until it is desired to shift
bypass assembly 132 to the disengaged position.
[0037] In the engaged position, bypass assembly 132 couples input
race 136 with output race 140 such that multimode clutch assembly
128 is in the bidirectional torque transfer mode. In this
configuration, secondary engine 114 may be operated in standby mode
or powered down as indicated by the dashed line between secondary
engine 114 and secondary gearbox 116 in FIG. 2C, such that main
engine 102 is driving not only the main drive system but also
accessories 124, as indicated by the arrows to secondary gearbox
116 and accessories 124. This configuration of powertrain 100 may
be referred to as a high efficiency configuration. In addition,
secondary engine 114 may be operated to provide supplemental power
to the main drive system as indicated by the arrow between
secondary gearbox 116 and the tail rotor drive shaft in FIG. 2D.
This configuration of powertrain 100 may be referred to as an
enhanced power configuration.
[0038] Continuing with the operating scenarios of helicopter 10,
once multimode clutch assembly 128 is in the bidirectional torque
transfer mode, helicopter 10 is ready for takeoff. Assuming a high
power demand takeoff and/or hover, powertrain 100 is preferably in
the enhanced power configuration of FIG. 2D for takeoff. Once
helicopter 10 has completed the takeoff and is flying at a standard
speed cruise, it may be desirable to place secondary engine 114 in
standby mode such as idle operations or even shut secondary engine
114 down to operate helicopter 10 in the high efficiency
configuration depicted in FIG. 2C. In this configuration, secondary
engine 114 provide no power as indicated by the dashed line between
secondary engine 114 and secondary gearbox 116 with torque and
rotational energy being provided by main engine 102 through the
main drive system to secondary gearbox 116 and accessories 124.
More specifically, power from the main drive system is transferred
through multimode clutch assembly 128 to output gear 126 by input
race 136 and output race 140 that are coupled together by bypass
assembly 132 then by shaft 122a and output race 122 of sprag clutch
118. Rotational energy is not sent to input race 120, as sprag
clutch 118 is operating in its overrunning mode. Thus, in addition
to powering main rotor 108 and tail rotor 112, in the high
efficiency configuration of powertrain 100, main engine 102 also
powers accessories 124.
[0039] It should be noted that multimode clutch assembly 128 is
preferably maintained in its bidirectional torque transfer mode
during all flight operations. For example, having multimode clutch
assembly 128 in its bidirectional torque transfer mode is a safety
feature of helicopter 10 in the event of a failure in main engine
102 during flight, as indicated by the dashed lines between main
engine 102 and sprag clutch 104 in FIG. 2E. In this case, an
autorotation maneuver may be performed in which the descent of
helicopter 10 creates an aerodynamic force on main rotor 108 as air
moves up through main rotor 108 generating rotational inertia. Upon
final approach during the autorotation landing, helicopter 10
performs a flare recovery maneuver in which the kinetic energy of
main rotor 108 is converted into lift using aft cyclic control.
Both the autorotation maneuver and the flare recovery maneuver are
enhanced by operating secondary engine 114 and sending power
through secondary gearbox 116 to the main drive system, as
indicated by the arrow therebetween, and more particularly by
sending power to main rotor 108 as indicated by the arrows leading
thereto. It is noted that rotational energy is also sent to sprag
clutch 104, which is operating in its overrunning mode while main
engine 102 is not operating. This configuration may be referred to
as the enhanced autorotation configuration of powertrain 100 in
which main engine 102 is not operating but secondary engine 114 is
providing power to main rotor 108 through multimode clutch assembly
128, which is in the bidirectional torque transfer mode.
[0040] Continuing with the operating scenarios of helicopter 10,
after a conventional landing, when it is desired to operate
multimode clutch assembly 128 from the bidirectional to the
unidirectional torque transfer mode, main engine 102 continues to
provide torque and rotational energy to input race 136, which in
turn drives output race 140 of sprag clutch 130. Actuator 154 then
provides a suitable disengagement signal (hydraulic, pneumatic,
electric) to operate cylinder 156 and shift piston 144 to the
position shown in FIG. 3A such that the outer splines of ring gear
132b shift out of mesh with inner splines 136a of input race 136,
thereby shifting bypass assembly 132 to the disengaged position.
Actuator assembly 134 preferably has a suitable locking mechanism
to maintain bypass assembly 132 in the disengaged position until it
is desired to shift bypass assembly 132 to the engaged
position.
[0041] Referring next to FIGS. 4A-4B, the lubrication strategy for
secondary gearbox 116 will now be described. Secondary gearbox 116
includes a lubrication circuit in which pressurized lubricating oil
is depicted as heavy dashed lines 200. The lubrication circuit
includes an oil pump (not pictured) that pressurizes and routes
lubricating oil to secondary gearbox 116 and in particular to
supply port 202. Pressurized lubricating oil 200 is then routed to
an annular passageway 204 defined between the housing of secondary
gearbox 116 and actuator liner 142 by a pair of seals depicted as
O-rings. Actuator liner 142 includes one or more passageways 206
that route pressurized lubricating oil 200 to an annular oil
chamber 208 defined between actuator liner 142 and piston 144 by a
pair of seals depicted as O-rings 144a, 144b. Pressurized
lubricating oil 200 then enters the interior of piston 144 via one
or more ports 210 that are in fluid communication with annular oil
chamber 208. From piston 144, pressurized lubricating oil 200 flows
into oil jet 146 that includes a plurality of nozzles 146a, 146b,
146c, 146d, 146e, 146f. A filter or debris screen (not pictured)
may be positioned within piston 144 to prevent any solids within
pressurized lubricating oil 200 from entering oil jet 146 and the
plugging nozzles.
[0042] Each of the nozzles directs pressurized lubricating oil 200
into a specific region within shaft 122a defined between adjacent
oil dams. More specifically, one or more nozzles 146a direct
pressurized lubricating oil 200 into region 212, one or more
nozzles 146b direct pressurized lubricating oil 200 into region
214, one or more nozzles 146c direct pressurized lubricating oil
200 into region 216, one or more nozzles 146d direct pressurized
lubricating oil 200 into region 218, one or more nozzles 146e
direct pressurized lubricating oil 200 into region 220 and one or
more nozzles 146f direct pressurized lubricating oil 200 into
region 222. The centrifugal force generated by rotation of shaft
122a during operation of helicopter 10 aids in oil flow from the
interior of shaft 122a to the desired locations within secondary
gearbox 116. For example, pressurized lubricating oil 200 from
region 212 flows to ball bearing set 152 for lubrication thereof.
Similarly, pressurized lubricating oil 200 from region 216 flows to
sprag clutch 130 to provide lubrication for the sprag elements 130a
between input race 136 and output race 140 as well as for clutch
bearing sets 130b, 130c. Oil dams within sprag clutch 130 keep
sprag elements 130a submerged in pressurized lubricating oil 200.
The oil dams may also include metering orifices that route
pressurized lubricating oil 200 to clutch bearing sets 130b, 130c.
Likewise, pressurized lubricating oil 200 from region 222 flows to
sprag clutch 118 to provide lubrication for the sprag elements 118a
between input race 120 and output race 122 as well as for clutch
bearing sets 118b, 118c. Oil dams within sprag clutch 118 keep
sprag elements 118a submerged in pressurized lubricating oil 200.
The oil dams may also include metering orifices that route
pressurized lubricating oil 200 to clutch bearing sets 118b, 118c.
Importantly, lubrication circuit integrity is maintained when
bypass assembly 132 is shifted between the engaged and disengaged
positions as the oil inlet to annular oil chamber 208 remains
between O-ring 144a, 144b as piston 144 shifts within actuator
liner 142 between the disengaged position of bypass assembly 132
(FIG. 4A) and the engaged position of bypass assembly 132 (FIG.
4B).
[0043] As discussed herein, multimode clutch assembly 128 is
preferably maintained in its bidirectional torque transfer mode
during all flight operations. This is achieved in the embodiment
depicted in FIGS. 5A-5B using a mechanical biasing element that
maintains bypass assembly 132 in the engaged position unless a
disengagement force sufficient to overcome the engagement force of
the mechanical biasing element is applied. Specifically, a
secondary gearbox 300 includes sprag clutch 118 having input race
120 and output race 122 which is coupled to output gear 126 that
provides power to accessories 124. Secondary gearbox 300 also
includes a multimode clutch assembly 128 that is coaxially aligned
with sprag clutch 118. Multimode clutch assembly 128 has a
unidirectional torque transfer mode and a bidirectional torque
transfer mode. Multimode clutch assembly 128 includes sprag clutch
130, bypass assembly 132 and an actuator assembly 302. Sprag clutch
130 includes input race 136 that is coupled to main rotor gearbox
106 via the tail rotor drive shaft and one or more gears including
input gear 138. Sprag clutch 130 includes output race 140 that is
coupled to output race 122 of sprag clutch 118 via shaft 122a.
Sprag clutch 130 may act as a one-way clutch enabling a driving
mode in which torque from the main drive system is coupled through
sprag clutch 130 from input race 136 to output race 140. Sprag
clutch 130 also has an overrunning mode in which the main drive
system is decoupled from torque transfer with sprag clutch 130 when
the rotating speed of input race 136 is less than the rotating
speed of output race 140 of sprag clutch 130. When sprag clutch 130
is acting as a one-way clutch, multimode clutch assembly 128 is in
its unidirectional torque transfer mode. In the unidirectional
torque transfer mode of multimode clutch assembly 128, torque can
be driven from the main drive system through secondary gearbox 300
but torque cannot be driven from secondary gearbox 300 to the main
drive system of powertrain 100.
[0044] The overrunning mode of multimode clutch assembly 128 can be
disabled by engaging bypass assembly 132 to couple input race 136
and output race 140 of sprag clutch 130 to functionally form a
connected shaft. In this configuration with bypass assembly 132
preventing sprag clutch 130 from operating in the overrunning mode,
multimode clutch assembly 128 is in its bidirectional torque
transfer mode. In the bidirectional torque transfer mode of
multimode clutch assembly 128, torque can be driven from the main
drive system through secondary gearbox 300 and torque can be driven
from secondary gearbox 300 to the main drive system of powertrain
100.
[0045] Multimode clutch assembly 128 is operated between the
unidirectional and bidirectional torque transfer modes by shifting
bypass assembly 132 between its disengaged position (FIG. 5A) and
its engaged position (FIG. 5B). The operations of engaging and
disengaging bypass assembly 132 may be pilot controlled and/or may
be automated by the flight control computer of helicopter 10 and
may be determined according to the operating conditions of
helicopter 10. In the illustrated embodiment, bypass assembly 132
is shifted between the engaged and disengaged positions responsive
to engagement and disengagement forces supplied by actuator
assembly 302.
[0046] Actuator assembly 302 includes an actuator liner 304 that is
fixed relative to the housing of secondary gearbox 300. A piston
306 is slidably and sealingly received within actuator liner 304.
In the illustrated embodiment, piston 306 is coupled to a piston
extension depicted as oil jet 146. Actuator assembly 302 also
includes a bearing sled 308 that is slidably received about
actuator liner 304. Bearing sled 308 is coupled to piston 306 to
prevent relative translation therebetween and thus, may be
considered part of piston 306. In the illustrated embodiment, a
mechanical biasing element depicted as wave spring 310 is
positioned between a shoulder of actuator liner 304 and an end of
bearing sled 308. A bearing assembly depicted as ball bearing set
152 couples bearing sled 308 with bypass assembly 132 such that
bypass assembly 132 is rotatable relative to bearing sled 308 as
well as the other components of actuator assembly 302. In addition,
actuator assembly 302 includes an actuator 312 having a cylinder
314 that is shiftable responsive to an electric signal, a hydraulic
signal, a pneumatic signal or the like. In the illustrated
embodiment, actuator assembly 302 has an energized configuration in
which cylinder 314 is retracted, as depicted in FIG. 5A, and an
unenergized or default configuration in which cylinder 314 is
released, as depicted in FIG. 5B.
[0047] When actuator 312 is not activated, the biasing force
generated by wave spring 310 acts on bearing sled 308 and serves as
an engagement force to shift bypass assembly 132 from the
disengaged position (FIG. 5A) to the engaged position (FIG. 5B). In
addition, once bypass assembly 132 is in the engaged position, the
biasing force generated by wave spring 310 continues to act on
bearing sled 308 to maintain the engagement force on bypass
assembly 132, thereby preventing bypass assembly 132 from shifting
out of the engaged position. The use of actuator assembly 302 with
wave spring 310 makes multimode clutch assembly 128 a mechanically
failsafe multimode clutch assembly that remains in the
bidirectional torque transfer mode even if a failure occurs in a
related electric, hydraulic and/or pneumatic system. When
helicopter 10 has landed and it is desired to shift bypass assembly
132 from the engaged position (FIG. 5B) to the disengaged position
(FIG. 5A), actuator 312 is energized with the appropriate electric
signal, hydraulic signal, pneumatic signal or the like to generate
a disengagement force that overcomes the engagement force of wave
spring 310 causing cylinder 314 to shift piston 306 relative to
actuator liner 304 which compresses wave spring 310 between
actuator liner 304 and bearing sled 308 and shifts bypass assembly
132 to the disengaged position. In the illustrated embodiment,
actuator 312 must remain energized to overcome the engagement force
of wave spring 310. Actuator assembly 302 may have a suitable
locking mechanism to secure bypass assembly 132 in the disengaged
position until it is desired to shift bypass assembly 132 to the
engaged position, in which case, actuator assembly 302 may be
deenergized after the locking mechanism has been deployed.
[0048] Alternatively or additionally, actuator 312 may be used to
provide at least a portion of the engagement force to shift bypass
assembly 132 from the disengaged position (FIG. 5A) to the engaged
position (FIG. 5B). For example, actuator 312 may be energized with
the appropriate electric signal, hydraulic signal, pneumatic signal
or the like to generate at least a portion of the engagement force
that together with the biasing force generated by wave spring 310
shifts bypass assembly 132 from the disengaged position to the
engaged position. In this embodiment, once bypass assembly 132 is
in the engaged position, actuator 312 may be unenergized as the
biasing force generated by wave spring 310 continues to act on
bearing sled 308 to maintain the engagement force on bypass
assembly 132, thereby preventing bypass assembly 132 from shifting
out of the engaged position.
[0049] FIGS. 6A-6B depict another embodiment of a secondary gearbox
that includes a failsafe multimode clutch assembly. In this
embodiment, a pressurized fluid maintains bypass assembly 132 in
the engaged position unless a disengagement force sufficient to
overcome the engagement force of the pressurized fluid is applied.
Specifically, secondary gearbox 400 includes sprag clutch 118
having input race 120 and output race 122 which is coupled to
output gear 126 that provides power to accessories 124. Secondary
gearbox 400 also includes a multimode clutch assembly 128 that is
coaxially aligned with sprag clutch 118. Multimode clutch assembly
128 has a unidirectional torque transfer mode and a bidirectional
torque transfer mode. Multimode clutch assembly 128 includes sprag
clutch 130, bypass assembly 132 and an actuator assembly 402. Sprag
clutch 130 includes input race 136 that is coupled to main rotor
gearbox 106 via the tail rotor drive shaft and one or more gears
including input gear 138. Sprag clutch 130 includes output race 140
that is coupled to output race 122 of sprag clutch 118 via shaft
122a. Sprag clutch 130 may act as a one-way clutch enabling a
driving mode in which torque from the main drive system is coupled
through sprag clutch 130 from input race 136 to output race 140.
Sprag clutch 130 also has an overrunning mode in which the main
drive system is decoupled from torque transfer with sprag clutch
130 when the rotating speed of input race 136 is less than the
rotating speed of output race 140 of sprag clutch 130. When sprag
clutch 130 is acting as a one-way clutch, multimode clutch assembly
128 is in its unidirectional torque transfer mode. In the
unidirectional torque transfer mode of multimode clutch assembly
128, torque can be driven from the main drive system through
secondary gearbox 400 but torque cannot be driven from secondary
gearbox 400 to the main drive system of powertrain 100.
[0050] The overrunning mode of multimode clutch assembly 128 can be
disabled by engaging bypass assembly 132 to couple input race 136
and output race 140 of sprag clutch 130 to functionally form a
connected shaft. In this configuration with bypass assembly 132
preventing sprag clutch 130 from operating in the overrunning mode,
multimode clutch assembly 128 is in its bidirectional torque
transfer mode. In the bidirectional torque transfer mode of
multimode clutch assembly 128, torque can be driven from the main
drive system through secondary gearbox 400 and torque can be driven
from secondary gearbox 400 to the main drive system of powertrain
100.
[0051] Multimode clutch assembly 128 is operated between the
unidirectional and bidirectional torque transfer modes by shifting
bypass assembly 132 between its disengaged position (FIG. 6A) and
its engaged position (FIG. 6B). The operations of engaging and
disengaging bypass assembly 132 may be pilot controlled and/or may
be automated by the flight control computer of helicopter 10 and
may be determined according to the operating conditions of
helicopter 10. In the illustrated embodiment, bypass assembly 132
is shifted between the engaged and disengaged positions responsive
to engagement and disengagement forces supplied by actuator
assembly 402.
[0052] Actuator assembly 402 includes an actuator liner 404 that is
fixed relative to the housing of secondary gearbox 400. A piston
406 is slidably and sealingly received within actuator liner 404.
In the illustrated embodiment, piston 406 is coupled to a piston
extension depicted as oil jet 146. Actuator assembly 402 also
includes a bearing sled 408 that is slidably received about
actuator liner 404 and that slidably receives piston 406 therein.
In the illustrated embodiment, a mechanical biasing element
depicted as wave spring 410 is positioned between a shoulder of
piston 406 and a shoulder of bearing sled 408. Wave spring 410
operates in a manner similar to wave spring 150 discussed herein to
assist in overcoming any misalignment in the clocking between
splines of bypass assembly 132 and input race 136 during engagement
operations. A bearing assembly depicted as ball bearing set 152
couples bearing sled 408 with bypass assembly 132 such that bypass
assembly 132 is rotatable relative to bearing sled 408 as well as
the other components of actuator assembly 402. In addition,
actuator assembly 402 includes an actuator 412 having a cylinder
414 that is shiftable responsive to an electric signal, a hydraulic
signal, a pneumatic signal or the like. In the illustrated
embodiment, actuator assembly 402 has an energized configuration in
which cylinder 414 is retracted, as depicted in FIG. 6A, and an
unenergized or default configuration in which cylinder 414 is
released, as depicted in FIG. 6B.
[0053] Similar to the lubrication circuit described herein with
reference to FIGS. 4A-4B, secondary gearbox 400 includes a
lubrication circuit that not only provides pressurized lubricating
oil to various components within secondary gearbox 400 but also
provides a pressure source for failsafe operations of bypass
assembly 132. In particular, the lubrication circuit of secondary
gearbox 400 includes an oil pump (not pictured) that pressurizes
and routes lubricating oil 416 to supply port 418. Pressurized
lubricating oil 416 is then routed to an annular passageway 420
defined between the housing of secondary gearbox 400 and actuator
liner 404 by a pair of seals depicted as O-rings. Actuator liner
404 includes one or more passageways 422 that route pressurized
lubricating oil 416 to an annular oil chamber 424 defined between
actuator liner 404 and piston 406 by a pair of seals depicted as
O-rings 406a, 406b. While not illustrated, pressurized lubricating
oil 416 then enters the interior of piston 406 for distribution to
various components via nozzles of oil jet 146, as discussed herein.
In the illustrated embodiment, annular oil chamber 424 and O-rings
406a, 406b defined a differential pressure chamber as the annular
area defined by O-ring 406b is larger than the annular area defined
by O-ring 406a such that when pressurized lubricating oil 416 flows
through annular oil chamber 424, a biasing force is generated that
acts on piston 406 and serves as an engagement force to shift
bypass assembly 132 from the disengaged position (FIG. 6A) to the
engaged position (FIG. 6B). In addition, once bypass assembly 132
is in the engaged position, the biasing force generated by
pressurized lubricating oil 416 in annular oil chamber 424
continues to act on piston 406 to maintain the engagement force on
bypass assembly 132, thereby preventing bypass assembly 132 from
shifting out of the engaged position.
[0054] The use of actuator assembly 402 with pressurized
lubricating oil 416 in annular oil chamber 424 makes multimode
clutch assembly 128 a hydraulically failsafe multimode clutch
assembly that remains in the bidirectional torque transfer mode
even if a failure occurs in a related electric, hydraulic and/or
pneumatic system. When helicopter 10 has landed and it is desired
to shift bypass assembly 132 from the engaged position (FIG. 6B) to
the disengaged position (FIG. 6A), actuator 412 is energized with
the appropriate electric signal, hydraulic signal, pneumatic signal
or the like to generate a disengagement force that overcomes the
engagement force of pressurized lubricating oil 416 in annular oil
chamber 424 causing cylinder 414 to shift piston 406 relative to
actuator liner 404 which in turn shifts bypass assembly 132 to the
disengaged position. In the illustrated embodiment, actuator 412
must remain energized to overcome the engagement force of
pressurized lubricating oil 416 in annular oil chamber 424.
Actuator assembly 402 may have a suitable locking mechanism to
secure bypass assembly 132 in the disengaged position until it is
desired to shift bypass assembly 132 to the engaged position, in
which case, actuator assembly 402 may be deenergized after the
locking mechanism has been deployed.
[0055] Alternatively or additionally, actuator 412 may be used to
provide at least a portion of the engagement force to shift bypass
assembly 132 from the disengaged position (FIG. 6A) to the engaged
position (FIG. 6B). For example, actuator 412 may be energized with
the appropriate electric signal, hydraulic signal, pneumatic signal
or the like to generate at least a portion of the engagement force
that together with the biasing force generated by pressurized
lubricating oil 416 in annular oil chamber 424 shifts bypass
assembly 132 from the disengaged position to the engaged position.
In this embodiment, once bypass assembly 132 is in the engaged
position, actuator 412 may be unenergized as the biasing force
generated by pressurized lubricating oil 416 in annular oil chamber
424 continues to act on piston 406 to maintain the engagement force
on bypass assembly 132, thereby preventing bypass assembly 132 from
shifting out of the engaged position.
[0056] As discussed herein, maintaining bypass assembly 132 in the
engaged position during all flight operations is an important
safety feature of the present helicopter to ensure, for example,
that the secondary engine can provide power to the main rotor in
the event of a main engine failure. Depending upon the specific
configuration of the multimode clutch assembly, a variety of
engagement status sensors may be used to monitor the engagement
status of the multimode clutch assembly. In one example, FIG. 7A
depicts secondary gearbox 116 with bypass assembly 132 in the
engaged position. In the illustrated embodiment, multimode clutch
assembly 128 includes one or more proximity sensors depicted as one
or more load cells 500. Load cells 500 may be coupled to an end of
shaft 122a such that translation of bypass assembly 132 brings an
end of shaft 132a into contact with load cells 500 when bypass
assembly 132 is in the engaged position. In one example, load cells
500 may be compression load cells having strain gauges that provide
an electrical signal to indicate the presence or absence of a load
and/or an absolute load between a no-load condition and a
full-capacity load. Such compression load cells may also be
referred to herein as strain sensors. In operation, a no-load
reading by load cells 500 indicates bypass assembly 132 is not in
the engaged position while a load reading indicates bypass assembly
132 is in the engaged position, thereby providing the engagement
status of bypass assembly 132. Alternatively, a load reading below
a predetermined threshold by load cells 500 indicates bypass
assembly 132 is not in the engaged position while a load reading
above a predetermined threshold indicates bypass assembly 132 is in
the engaged position, thereby providing the engagement status of
bypass assembly 132.
[0057] In another example, FIG. 7B depicts secondary gearbox 116
with bypass assembly 132 in the engaged position. In the
illustrated embodiment, multimode clutch assembly 128 includes one
or more engagement status sensors depicted as one or more tooth
passage frequency sensors 502. For example, tooth passage frequency
sensors 502 could be variable reluctance sensors, monopole sensors,
hall-effect sensors, optical sensors or the like. In the
illustrated embodiment, bypass assembly 132 includes two ring gears
132b, 132c. The number of splines on ring gear 132b is different
from the number of teeth on ring gear 132c such as in a ratio of 2
or 3 to 1 or in a ratio of 1 to 2 or 3. When bypass assembly 132 is
in the engaged position, tooth passage frequency sensors 502 are
aligned with rotating ring gear 132c such that the alternating
presence and absence of the passing gear teeth has a first
frequency. When bypass assembly 132 is in the disengaged position,
tooth passage frequency sensors 502 are aligned with rotating ring
gear 132b which has a different number of splines than the number
of teeth of ring gear 132c such that the alternating presence and
absence of the passing splines has a second frequency. The
frequency detected by tooth passage frequency sensors 502 is
different for ring gear 132b versus ring gear 132c such that the
change in frequency and/or the absolute frequency provides the
engagement status of bypass assembly 132.
[0058] When tooth passage frequency sensors 502 are variable
reluctance sensors, for example, the alternating presence and
absence of the passing gear teeth vary the reluctance of a magnetic
field, which dynamically changes the magnetic field strength. This
changing magnetic field strength induces a current into a coil
winding which is attached to the output terminals such that the
variable reluctance sensors provide a frequency output.
Alternatively or additionally, tooth passage frequency sensors 502
may be used to detect a change in the annular speed of bypass
assembly 132 in the engaged position versus the disengage position,
even in embodiments having the same number of teeth on both ring
gears 132b, 132c. In this implementation, tooth passage frequency
sensors 502 provide a first frequency reading when bypass assembly
132 is in the engaged position and a second frequency reading,
based upon a lower or a higher annular speed of bypass assembly 132
depending upon the status of secondary engine 114, when bypass
assembly 132 is in the disengaged position, thereby providing the
engagement status of bypass assembly 132.
[0059] In a further example, FIG. 7C depicts secondary gearbox 300
with bypass assembly 132 in the engaged position. In the
illustrated embodiment, multimode clutch assembly 128 includes one
or more oil pressure sensors 504 which may be positioned within
actuator liner 304 or may be otherwise located within the secondary
gearbox downstream of an oil pressure passageway. Oil pressure
sensors 504 are selectively aligned with one or more ports 506 of
piston 306 that are in communication with the lubrication circuit
of secondary gearbox 300 to detect the presence or absence of oil
pressure and/or a high pressure or low pressure condition.
Specifically, when bypass assembly 132 is in the disengaged
position, ports 506 are not aligned with oil pressure sensors 504
whereas, when bypass assembly 132 is in the engaged position, ports
506 are aligned with oil pressure sensors 504. A pressure reading
below a predetermined threshold by oil pressure sensors 504
indicates bypass assembly 132 is not in the engaged position while
a pressure reading above a predetermined threshold indicates bypass
assembly 132 is in the engaged position, thereby providing the
engagement status of bypass assembly 132.
[0060] FIG. 7D depicts secondary gearbox 300 with bypass assembly
132 in the engaged position. In the illustrated embodiment,
multimode clutch assembly 128 includes an engagement status sensor
depicted as a variable differential transformer in the form of a
linear variable differential transformer 508. Linear variable
differential transformer 508 includes a core 508a that is coupled
to the end of oil jet 146 that translates within a coil assembly
508b such that an input voltage within coil assembly 508b induces
two output voltages as piston 306 is shifted between first and
second positions. The electrical signals generated in responsive to
the rectilinear motion of core 508a relative to coil assembly 508b
is used to determine the engagement status of bypass assembly
132.
[0061] FIG. 7E depicts secondary gearbox 300 with bypass assembly
132 in the engaged position. In the illustrated embodiment,
multimode clutch assembly 128 includes an engagement status sensor
depicted as a variable differential transformer in the form of a
rotary variable differential transformer 510. An input shaft of
rotary variable differential transformer 510 is rotated by gear
teeth 512 on piston 306 as piston 306 is shifted between first and
second positions. Rotary variable differential transformer 510
provides a variable alternating current output voltage that is
linearly proportional to the angular displacement of the input
shaft. These electrical signals are used to determine the
engagement status of bypass assembly 132.
[0062] The foregoing description of embodiments of the disclosure
has been presented for purposes of illustration and description. It
is not intended to be exhaustive or to limit the disclosure to the
precise form disclosed, and modifications and variations are
possible in light of the above teachings or may be acquired from
practice of the disclosure. The embodiments were chosen and
described in order to explain the principals of the disclosure and
its practical application to enable one skilled in the art to
utilize the disclosure in various embodiments and with various
modifications as are suited to the particular use contemplated.
Other substitutions, modifications, changes and omissions may be
made in the design, operating conditions and arrangement of the
embodiments without departing from the scope of the present
disclosure. Such modifications and combinations of the illustrative
embodiments as well as other embodiments will be apparent to
persons skilled in the art upon reference to the description. It
is, therefore, intended that the appended claims encompass any such
modifications or embodiments.
* * * * *